Safe robot with trajectory progress variables

Abstract

A method for controlling a multiaxial jointed-arm robot. A plurality of reference data sets are recorded during a previous monitored reference travel. During an operational travel, a trajectory progress variable is established and is used to monitor the movement of the manipulator on the basis of the reference data sets.

The invention claimed is: 
     
       1. A method for controlling a manipulator by a programmable controller having access to a plurality of reference data sets, with every reference data set describing a reference manipulator position along a predetermined path defined by a trajectory plan, each reference manipulator position describing the position of individual joints of the manipulator in the reference manipulator position, the programmable controller performing the steps of:
 recording an actual manipulator position during an operation of the manipulator, the actual manipulator position describing the position of individual joints of the manipulator in the manipulator in the actual manipulator positions; 
 determining a value for an actual trajectory progress variable (actual TPV), wherein the value is determined as a function of the recorded actual manipulator position and a previously recorded actual manipulator position and is independent of any speed characteristic of the manipulator; 
 selecting a reference manipulator position from at least one of the plurality of reference data sets, the reference manipulator position selected by comparing a value of a TPV for the selected reference manipulator position with the value of the determined actual TPV; 
 determining whether a difference between the selected reference manipulator position and the recorded actual manipulator position is greater than a pre-defined limit value, and 
 stopping movement of the actual manipulator position when the difference is greater than the pre-defined limit value. 
 
     
     
       2. The method according to  claim 1 , wherein the method comprises introducing a response strategy when the difference is less than or equal to the pre-defined limit value. 
     
     
       3. The method according to  claim 1 , wherein a reference trajectory progress variable (reference TPV) is assigned to every reference data set, and further wherein the reference TPV assigned to each reference data set has a unique value. 
     
     
       4. The method according to  claim 3 , wherein the selection of the reference manipulator position comprises selecting the reference manipulator position such that the value of the reference TPV of the reference data set for the selected reference manipulator position is closest among the reference TPV values of the plurality of reference data sets to the determined value for the actual TPV. 
     
     
       5. The method according to  claim 3 , wherein the selection of the reference manipulator position comprises:
 selecting at least two different reference data sets such that the values of the reference TPVs for each of the selected reference data sets are closest among the reference TPV values of the plurality of reference data sets to the determined actual TPV, and 
 calculating a reference manipulator position based on an interpolation between the reference manipulator positions of the selected reference data sets. 
 
     
     
       6. The method according to  claim 3 , the value of the actual TPV and values for each reference TPV are scalar values. 
     
     
       7. The method according to  claim 1 , wherein the determination of the value of the actual TPV is additionally based on the value of a previously recorded actual TPV. 
     
     
       8. The method according to  claim 1 , wherein every reference manipulator position comprises reference axis values describing the positions of the individual joints of the manipulator and wherein every actual manipulator position comprises actual axis values describing the positions of the individual joints. 
     
     
       9. The method according to  claim 8 , wherein the determination of the value of the actual TPV comprises:
 determining differences between each of the axis values for the recorded actual manipulator position and corresponding axis values for the previously recorded actual manipulator position; and 
 summing the absolute values of the differences between the axis values. 
 
     
     
       10. The method according to  claim 9 , wherein the determination of the actual TPV additionally comprises adding the absolute values of the differences between the axis values to a previously recorded actual TPV. 
     
     
       11. The method according to  claim 1 , wherein the manipulator includes sensors and every reference manipulator position and the recorded actual manipulator position additionally comprise sensor data, wherein the sensors preferably comprise torque sensors and the sensor data comprises torques. 
     
     
       12. The method according to  claim 1 , wherein the trajectory plan of the manipulator is divided into several movement sets each having a reference set number, and wherein a corresponding one of the movement set numbers is assigned as a reference movement set number to each reference data set, wherein at least two reference data sets have the same reference movement set number, and wherein each reference data set with the same reference movement set number is assigned a different reference TPV. 
     
     
       13. The method according to  claim 12 , additionally including assigning a corresponding one of the movement set numbers as an actual movement set number and recording the actual movement set number, wherein the identification of the reference manipulator position is additionally based on matching the reference set number of the reference manipulator position to the recorded actual movement set number. 
     
     
       14. The method according to  claim 1 , wherein the provision of the plurality of reference data sets includes:
 travelling of the manipulator; 
 recording of a plurality of reference manipulator positions; 
 determining, for every reference manipulator position, of a reference TPV, and 
 generating a plurality of reference data sets, with every reference data set describing one of the recorded reference manipulator positions and every reference data set is assigned one of the determined reference TPVs. 
 
     
     
       15. The method according to  claim 1 , wherein the steps of recording, determining, selecting and determining are repeatedly performed during each of a plurality of interpolation cycles, and the determination of the value of the actual TPV in a current one of the plurality of interpolation cycles is additionally based on of the value of an actual TPV recorded in a prior cycle to the current interpolation cycle. 
     
     
       16. The method according to  claim 1 , wherein the steps of recording determining, selecting and determining are repeatedly performed during each of a plurality of interpolation cycles, and the determination of the value of the actual TPV in a current one of the plurality of interpolation cycles is additionally based on the value of an actual TPV recorded in an immediately prior cycle to the current interpolation cycle. 
     
     
       17. A robot system comprising;
 a manipulator; and 
 a controller configured to:
 record an actual manipulator position during an operation of the manipulator, 
 determine a value for an actual trajectory progress variable (actual TPV), wherein the value is determined as a function of the recorded actual manipulator position and a previously recorded actual manipulator position and is independent of any speed characteristic of the manipulator, 
 select a reference manipulator position from at least one of a plurality of reference data sets, wherein each one of the plurality of reference data sets describes a reference manipulator position along a predetermined path defined by a trajectory plan and the selected reference manipulator position is selected by comparing a value of a TPV for the selected reference manipulator position with the value of the determined actual TPV, 
 determine whether a difference between the identified reference manipulator position and the recorded actual manipulator position is greater than a pre-defined limit value, and 
 stop movement of the actual manipulator position when the difference is greater than the pre-defined limit value. 
 
 
     
     
       18. The robot system according to  claim 17 , wherein the controller is configured to introduce a response strategy when the difference is less than or equal to the pre-defined limit value. 
     
     
       19. The robot system according to  claim 17 , wherein a reference trajectory progress variable (reference TPV) is assigned to every reference data set, and further wherein the reference TPV assigned to each reference data set has a unique value. 
     
     
       20. The robot system according to  claim 19 , wherein the controller is configured to select the reference manipulator position such that the value of the reference TPV of the reference data set for the selected reference manipulator position is closest to the determined actual TPV. 
     
     
       21. The robot system according to  claim 19 , wherein the controller is configured to select the reference manipulator position by:
 selecting at least two different reference data sets such that the values of reference TPVs for each of the selected reference data sets are closest among the reference TPV values of the plurality of reference data sets to the determined actual TPV, and 
 calculating a reference manipulator position based on an interpolation between the reference manipulator positions of the selected reference data sets. 
 
     
     
       22. The robot system according to  claim 19 , wherein the value of the actual TPV and values for each reference TPV are scalar values. 
     
     
       23. The robot system according to  claim 17 , wherein the controller is configured to determine the value of the actual TPV based additionally on the value of a previously recorded actual TPV. 
     
     
       24. The robot system according to  claim 17 , wherein every reference manipulator position comprises reference axis values describing the positions of the individual joints of the manipulator and wherein every actual manipulator position comprises actual axis values describing the positions of the individual joints. 
     
     
       25. The robot system according to  claim 24 , wherein the controller is configured to determine the actual TPV by:
 determining differences between each of the axis values for the recorded actual manipulator position and corresponding axis values for the previously recorded actual manipulator position; and 
 summing the absolute values of the differences between the axis values. 
 
     
     
       26. The robot system according to  claim 25 , wherein the controller is configured to determine the actual TPV additionally by adding the absolute values of the differences between the axis values to a previously recorded actual TPV. 
     
     
       27. The robot system according to  claim 17 , wherein the manipulator includes sensors and every reference manipulator position and the recorded actual manipulator position additionally comprise sensor data, wherein the sensors preferably comprise torque sensors and the sensor data comprises torques. 
     
     
       28. The robot system according to  claim 17 , wherein the trajectory plan of the manipulator is divided into several movement sets each having a reference set number, and wherein a corresponding one of the movement set numbers is assigned as a reference movement set number to each reference data set, wherein at least two reference data sets have the same reference movement set number, and wherein each reference data set with the same reference movement set number is assigned a different reference TPV. 
     
     
       29. The robot system according to  claim 28 , wherein the controller is configured in addition for assigning a corresponding one of the movement set numbers as an actual movement set number and recording the actual movement set number, and wherein the identification of the reference manipulator position is additionally based on matching the reference set number of the reference manipulator position to the recorded actual movement set number. 
     
     
       30. The robot system according to  claim 17 , wherein the controller is configured to provide the plurality of reference data sets by:
 moving the manipulator; 
 recording a plurality of reference manipulator positions; 
 determining, for every reference manipulator position, a reference TPV, and 
 generating a plurality of reference data sets, with every reference data set describing one of the recorded reference manipulator positions and assigning every reference data set to one of the determined reference TPVs.